1. Field of the Invention
The present invention relates to a gas venting floating cover for a liquid container.
2. Description of the Prior Art
Relatively large volumes of methane and other gases are generated in the processing of waste products in reservoirs or containers. Floating covers are often used to prevent the escape of such gases, a floating cover suitable for this purpose being described in U.S. Letters Patent Re. No. 30,146, reissued Nov. 13, 1979, and entitled "Floating Cover For A Liquid Storage Reservoir". A cover of this general type is made of flexible sheet material buoyed upon the liquid surface by a float system which is centrally located to enable excess material at the cover perimeter to form into a depending fold. The fold acts as a rainwater collection sump. The edges of the cover are attached to the reservoir sides or perimeter in generally fluid tight relation to collect any gases evolving from the liquid.
A system of the prior art for venting collected gases from beneath a water reservoir cover is described in U.S Letters Patent No. 3,980,199, issued Sept. 14, 1976, and entitled "Gas Venting For Floating Cover". This patent discloses a system of floats which define gas passages distributed throughout the underside of the cover for collecting such gas. In one embodiment the collected gas flows to a plurality of transverse conduits embedded in a continuous string of longitudinally extending floats. Each transverse conduit is connected to a separate vertical riser, and all of the risers are connected to a longitudinal pipe which carries the gas to the reservoir perimeter for handling. As a consequence of the multiplicity of transverse conduits and risers, the system is relatively time consuming and expensive to install and is incapable of handling relatively large volumes of gas, such as would be evolved in a food waste processing installation.
In another embodiment disclosed in U.S. Pat. No. 3,980,199, a string of longitudinal floats intersects a plurality of transverse strings of floats, the latter extending up the adjacent sloping sides of the reservoir so that gas collected in passages defined by the transverse floats can flow into a collection conduit installed at the reservoir sidewall. This embodiment can handle larger quantities of gas but has the disadvantage that the transverse float strap prevent the peripheral portion of the cover from forming into a depending rainwater collection sump. Consequently, rainwater tends to collect in separate pockets in the individual bays defined between the transverse float strings, and its removal is a tedious procedure.